I’m not talking about stubborn traits which twins have. I’m sure my twins will be no less stubborn than their older siblings.
I’m only really going to focus on one thing in this post which is to explain how types of twins are determined – in other words, how to know if they are identical vs non-identical.
In my post “Twin Pregnancy Diary – The top 10 twin pregnancy questions I’ve been asked so far”, question 4 was, “Are they identical?” to which I answered “It seems that they are most likely non-identical”.
I had no set answer.
This is why.
Twins can be either monozygotic or dizygotic, identical or non-identical.
Identical twins are monozygotic. They are created by a fertilised egg splitting any time within 14 days of fertilisation. Depending on when exactly during this time the egg splits will determine whether they will share sacs and placentas. Identical twins will always be the same sex and have the same dna.
Monozygotic twins who were created from a fertilised egg splitting from around 9-12 days will share the same sac and placenta and a single chorion and are referred to as Monochorionic/Monoamniotic (“mono” in Greek means “only” or “single”):
(I can tell that you are blown away by my technical drawings).
Identical twins can also be Monochorionic/Diamniotic which means they each have their own sac and placenta and a single chorion. Again, they will have been created by a single fertilised egg splitting but within 4-9 days of fertilisation:
Our twins are dichorionic/diamniotic which means that they each have their own sac and own placenta. This is the most favourable type of twin pregnancy to have as your babies are not at risk of getting caught up in each others cords or from TTTS (Twin to Twin Transfusion Syndrome – where one twin takes extra nourishment at the expense of the other and can be very dangerous to both babies). Here is my technical diagram:
Twin Pregnancy Diary is available to buy in paperback now.